Dallas City is a city in Hancock and Henderson counties in the U.S. state of Illinois. The population in 2020 stands at an estimate of 805, a decline from the 2010 census of 945, which was a decline from 1,055 in 2000. The Hancock County portion of Dallas City is part of the Fort Madison–Keokuk, IA–IL–MO Micropolitan Statistical Area, and the Henderson County portion of Dallas City is part of the Burlington, IA–IL Micropolitan Statistical Area.